With present technologies, in a wireless local area network (WLAN) having multiple access points (APs), a client device can be matched to the best AP in the WLAN. Nevertheless, how to achieve efficient roaming in a multi-AP wireless environment remains to be a challenge to be solved.
The Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards generally refers to a set of media access control (MAC) and physical layer (PHY) specifications for implementing wireless local area network (WLAN) computer communications. However, the IEEE 802.11 standards do not include any specifications for a multi-AP environment, but only specify how one or more client devices can communicate with a single AP in the WLAN.
Recent IEEE 802.11 proposals have been focusing on how to facilitate client device to make efficient roaming decisions. Nevertheless, the recent proposals typically rely on client devices to make decisions regarding which AP the client devices shall roam to. Over the past few years, client devices have become more intelligent at making roaming decisions. Yet no standardized roaming behavior is observed from the client devices in a WLAN.
When a client device is associated with an AP, the client device continuously scans through different wireless communication channels in the background to determine which other APs within the physical proximity of the client device are sending out signals advertising the same Service Set Identifier (SSID) as the AP that the client device is currently associated with. Therefore, if the connection between the client device and the current AP breaks, the client device already has the knowledge of other APs in the WLAN that it can connect to.
In a multi-AP environment, it is up to the client device to determine which AP to connect to when the connection between the client device and the current AP drops below a threshold level. On the other hand, the client device typically will choose an AP based on which AP is associated with the strongest signal strength at a particular point of time. This may lead to at least two potential problems. First, the AP chosen at the particular point of time may not be the best AP over a long term. Second, a client device will likely need to roam from one AP to another AP more frequently if the client device makes a poor choice regarding which AP to connect to.
Meanwhile, voice and video applications have become prevalent among client devices in WLANs. Specifically, smartphones nowadays have capabilities of transmitting both voice and data over the WLAN. Accordingly, roaming of such mobile client devices becomes an important issue, because users expect to have seamless mobility in mobile client devices. Hence, an efficient roaming mechanism for mobile client devices in a multi-AP environment is desirable.